The present invention is directed to the discovery of a clean, gas heating and re-circulating pumping system configuration that will quickly and efficiently heat a connected process chamber or process piping section. The useful application of the invention includes the removal of stubborn contaminants such as water vapor and hydrocarbons from the internal surfaces of a process vacuum chamber or process piping system. The invention utilizes the substantial heat generated and subsequently imparted to gas molecules that are agitated as they pass through the inlet and outlet of a dual rotor, multi-lobed, rotary gas compressor There are a variety of dual rotor, multi-lobed, rotary gas compressors that will perform the gas agitation/heating function of the invention, the most common being dual rotor, multi-lobed, rotary gas compressors such as roots or screw type pumps. The invention was developed using a dual rotor, 60 degree twist, three-lobe rotor, rotary gas compressor, although it is envisioned that there may be alternative pump geometries that will perform the invention functions even more efficiently. The invention heat generation through mechanical molecular gas agitation functions are: 1) Rapid agitation of gas molecules that pass through the inlet and outlet of the compressor/pump creating a substantial rise in gas temperature; 2) Rapid gas throughput to increase the frequency that the gas is agitated in a closed loop gas re-circulation system; 3) Rapid gas agitation and subsequent gas temperature rise with a minimal delta pressure compression ratio between the compressor inlet and exhaust to minimize the amount of energy required to drive the compressor; 4) The ability to operate over a wide pressure range to cover both positive and vacuum pressure applications. The use of dual rotor, multi-lobed, rotary gas compressor to quickly and efficiently raise gas temperature will have broad application as an economical source of convective heat in closed loop piping, commercial convection ovens, process vacuum systems, positive/vacuum pressure dehydration applications, and water and space heating.
"Background Art"
In order to generate convection heat, industry has relied on contact of a gas medium with a hot surface or flame. The heat imparted to the gas medium in this type of configuration is directly proportional to the amount of energy consumed to maintain the elevated temperature of the surface or the temperature of the flame that is in direct contact with the gas stream. Conversely, convection or gas contact heat has not been an energy efficient method to transfer heat to a surface due to the poor thermal transfer capability of gas in this type of heating configuration, although in special applications, such as the removal of certain types of contaminants such as molecular water vapor and hydrocarbon molecules from the internal surfaces of a vacuum system, cycle purging with a heated purge gas has been an efficient method. The most common method to remove the contamination has been the energy intensive application of external heat to the vacuum process chamber. This external heat baking to elevated temperatures as high as 400 degrees Fahrenheit is used in vacuum systems to reduce the dwell time of contaminants on the internal surfaces of a process system. The external baking is not always enough to provide successful removal of the contamination. When conventional configurations rely on vacuum to remove the contamination; the random motion of this molecular contamination in molecular flow vacuum conditions makes successful removal primarily a function of time. A successful prior art technique to reduce this time has been the introduction of a hot gas purge to sweep the inside surfaces of molecular contamination with a hot dry gas that will act as an effective transport mechanism for the contamination to the vacuum pumping subsystem. The effectiveness of the heated gas purge is improved through repeated purge cycles. In attempts to find a more efficient method to perform this hot gas purge function, it has been discovered the heat generation method of the invention, using a dual rotor, multi-lobed, rotary gas compressor to perform the molecular gas agitation function that can very quickly impart heat to a gas stream more efficiently than traditional methods that utilize contact with a hot surface.